In the human case, my understanding is that it's actually the opposite, pregnancy sex is highly recommended for the mutual enjoyment of all parties involved (not that the fetus would enjoy it per se, but it shouldn't be harmful actually)...

Frankly, I've never understood the whole "twin penile dragon" thing. If anatomy is to be believed, then wouldn't evolution have given female dragons two vaginas; one right on top of the other? Otherwise, what point is there for dragons to have two dicks?

Overall, it was a good fic. Maybe consider doing a fic with Krackle. (She's a girl dragon, right?) Have the story focus on her, with her two vaginas, in a gang bang. Maybe that could be the "party" that happens during the commercial break of the Dragon Quest episode. Spike's final test as a dragon is to bang Krackle with the other teen dragons.

Bonus points if Twilight, Rainbow Dash and Rarity watch it happen voyeuristically from their dragon disguise. Double the points if they join in while still wearing the costume. Then shit hits the fan when the disguise falls apart during the orgy and the dragons realize that "Krackle's cousin" was actually three ponies.

Disregarding that spat over on Animal Antics, I freaking loved this. It was absolutely terrific, and had the author requested just Spike and Trixie, it would have been absolutely beautiful. TrixiexSpike is disappointingly scarce, yet happens to be my favorite ship ever conceived. Had I known this existed, I would have read it ages ago. Although I wish it were a oneshot, the compilation of three is worth favoriting just for this one chapter.